Buggy code:
public class Change implements Serializable , Comparable < Change > { private List < String > AffectedClasses ; private String Course ; private String OldTeacher ; private String NewTeacher ; private String Subject ; private String Room ; private Integer Hour ; private String Remark ; public Change ( List < String > affectedClasses , String course , int hour , String subject , String oldTeacher , String newTeacher , String room , String remark ) { } public Change ( String affectedClass , String course , int hour , String subject , String oldTeacher , String newTeacher , String room , String remark ) { } public List < String > getAffectedClasses ( ) { } public String getOldTeacher ( ) { } public String getNewTeacher ( ) { } public String getRoom ( ) { } public Integer getHour ( ) { } public String getRemark ( ) { } public String getSubject ( ) { } public String getCourse ( ) { } public static void saveChangeList ( List < Change > changes , Date date , Context context ) { } public static List < Change > loadChangeList ( Date date , Context context ) throws JSONException { } @ Override public boolean equals ( Object changeObject ) { } @ Override public int compareTo ( Change change ) { } public String toString ( boolean isTeacher ) { if ( isTeacher ) { if ( Remark . contains ( "Raumänderung" ) ) { return ( ( ( Hour ) + ".<seq2seq4repair_space>Stunde:<seq2seq4repair_space>" ) + ( AffectedClasses . get ( 0 ) ) ) + ",<seq2seq4repair_space>Raumänderung" ; } else { return ( ( ( ( ( Hour ) + ".<seq2seq4repair_space>Stunde:<seq2seq4repair_space>" ) + ( AffectedClasses . get ( 0 ) ) ) + "<seq2seq4repair_space>statt<seq2seq4repair_space>" ) + ( OldTeacher ) ) + ",<seq2seq4repair_space>Vertretung" ; } } else { if ( ( ( Remark . contains ( "entfällt" ) ) || ( Remark . contains ( "Eigenstudium" ) ) ) || ( ( Room . isEmpty ( ) ) && ( NewTeacher . isEmpty ( ) ) ) ) { return ( ( ( ( ( Hour ) + ".<seq2seq4repair_space>Stunde:<seq2seq4repair_space>" ) + ( Subject ) ) + "<seq2seq4repair_space>bei<seq2seq4repair_space>" ) + ( OldTeacher ) ) + "<seq2seq4repair_space>entfällt" ; } else if ( Remark . contains ( "Raumänderung" ) ) { if ( Room . isEmpty ( ) ) { return ( ( ( ( ( Hour ) + ".<seq2seq4repair_space>Stunde:<seq2seq4repair_space>" ) + ( Subject ) ) + "<seq2seq4repair_space>bei<seq2seq4repair_space>" ) + ( OldTeacher ) ) + ",<seq2seq4repair_space>Raumänderung" ; } else { return ( ( ( ( ( ( ( Hour ) + ".<seq2seq4repair_space>Stunde:<seq2seq4repair_space>" ) + ( Subject ) ) + "<seq2seq4repair_space>bei<seq2seq4repair_space>" ) + ( OldTeacher ) ) + ",<seq2seq4repair_space>Raumänderung<seq2seq4repair_space>(" ) + ( Room ) ) + ")" ; } } else <START_BUG> if ( getNewTeacher ( ) . isEmpty ( ) ) { <END_BUG> return ( ( ( ( ( ( ( Hour ) + ".<seq2seq4repair_space>Stunde:<seq2seq4repair_space>" ) + ( Subject ) ) + "<seq2seq4repair_space>bei<seq2seq4repair_space>" ) + ( OldTeacher ) ) + ",<seq2seq4repair_space>" ) + ( NewTeacher ) ) + "<seq2seq4repair_space>vertritt" ; } else { return ( ( ( ( ( Hour ) + ".<seq2seq4repair_space>Stunde:<seq2seq4repair_space>" ) + ( Subject ) ) + "<seq2seq4repair_space>bei<seq2seq4repair_space>" ) + ( OldTeacher ) ) + ",<seq2seq4repair_space>Vertretung" ; } } } public String toStringDebug ( ) { } }

Fix:
if ( ! ( NewTeacher . isEmpty ( ) ) ) {